这些行必须在OnCreate中:

mmAdapter = new Adapter(msgList);
mrecyclerView.setAdapter(mmAdapter);

这对我很管用。

如果您正在使用模拟器，请执行此操作。

android：usesCleartextTraffic=“true”

如果你的cardviewxml设计是这样的，

android.support.v7.widget.CardView

用android x替换cardviewxml设计。 必须如此;

androidx.cardview.widget.CardView

如果你的recyclerview xml设计是这样的，

android.support.v7.widget.RecyclerView

用android x替换cardviewxml设计。 必须如此;

androidx.recyclerview.widget.RecyclerView

我也犯了同样的错误，我修复了它如果你像我一样在等待数据，使用改造或类似的东西

放在Oncreate之前

private ArtistArrayAdapter adapter;
private RecyclerView recyclerView;

把它们放在Oncreate中

 recyclerView = (RecyclerView) findViewById(R.id.cardList);
 recyclerView.setHasFixedSize(true);
 recyclerView.setLayoutManager(new LinearLayoutManager(this));
 adapter = new ArtistArrayAdapter( artists , R.layout.list_item ,getApplicationContext());
 recyclerView.setAdapter(adapter);

当你收到数据时放

adapter = new ArtistArrayAdapter( artists , R.layout.list_item ,getApplicationContext());
recyclerView.setAdapter(adapter);

现在进入ArtistArrayAdapter类，执行这个操作它会做的是如果数组为空或为空它会让GetItemCount返回0如果不是它会让它成为艺术家数组的大小

@Override
public int getItemCount() {

    int a ;

    if(artists != null && !artists.isEmpty()) {

        a = artists.size();
    }
    else {

        a = 0;

     }

   return a;
}

检查是否错过了在适配器中调用此方法

@Override
public int getItemCount() {
    return list.size();
}

在我的布局xml文件中，缺少了带有layoutManager的底线。我添加后错误消失了。

   <androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recycler_view_chat"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1"
    app:layoutManager="LinearLayoutManager"/>

 override fun onCreateView(...  ): View? 
   {
        val rootview = inflater.inflate(R.layout.fragment_menu, 
        container,false)

        val recycler_menu_list = 
         rootview.findViewById(R.id.recycler_menu_list) as RecyclerView

        recycler_menu_list.layoutManager = LinearLayoutManager(activity)

        val data =  ...

        foodCardAdapter = FoodCardAdapter()

        recycler_menu_list.adapter=foodCardAdapter

        foodCardAdapter.submitList(data)      

       //make sure that the return view is one declared above up and is 
       //not the default 'inflater.inflate(R.layout.fragment_menu,         
       //container,false)' created by the ide

        return rootview    
    }